3.3.10.3 : SubHalo

The table stores all the subhalos identified with the SUBFIND algorithm in the friends-of-friends groups
identified within the Millennium-II Simulation
of the FOF groups themselves are stored in the
FOF table.

column

type

UCD

unit

description

subHaloId

long

meta.id;

The id of this subhalo based on its rank within its parent FOF halo.

fofId

long

meta.id;

The id of FOF group this subhalo belongs to.

subHaloFileId

long

meta.id;

Alternative id of this subhalo based on its rank within the SUBFIND result file.

snapNum

int

time

The snapshot number where this subhalo was identified.
This column corresponds to the snapnum column in
the Snapshots table in the Millennium-II database.

redshift

float

time

The redshift of the snapshot to which this subhalo belongs.

np

int

meta.number

Number of simulation particles in this subhalo.

mass

real

1010 Msun/h

Mass of this subhalo, given by the product of the number of particles and the mass per particle.

x

float

pos.cartesian.x

Mpc/h

The X-coordinate of the position, determined by the particle with the minimum gravitational potential, in comoving coordinates.

y

float

pos.cartesian.y

Mpc/h

The Y-coordinate of the position, determined by the particle with the minimum gravitational potential, in comoving coordinates.

z

float

pos.cartesian.z

Mpc/h

The Z-coordinate of the position, determined by the particle with the minimum gravitational potential, in comoving coordinates.

ix

integer

pos.cartesian.x

Zone index along x-direction, based on 20 bins
See the text on spatial indexes.

iy

integer

pos.cartesian.x

Zone index along y-direction, based on 20 bins
See the text on spatial indexes.

iz

integer

pos.cartesian.x

Zone index along z-direction, based on 20 bins
See the text on spatial indexes.

phKey

int

The Peano-Hilbert index for the position of this subhalo.

velX

float

phys.veloc

km/sec

The X-component of the peculiar velocity.

velY

float

phys.veloc

km/sec

The Y-component of the peculiar velocity.

velZ

float

phys.veloc

km/sec

The Z-component of the peculiar velocity.

cmx

float

Mpc/h

The X-coordinate of the subhalo's center of mass, in comoving coordinates.

cmy

float

Mpc/h

The Y-coordinate of the subhalo's center of mass, in comoving coordinates.

cmz

float

Mpc/h

The Z-coordinate of the subhalo's center of mass, in comoving coordinates.

spinX

float

phys.veloc.ang

(Mpc/h) (km/sec)

The X-component of the spin of the subhalo.

spinY

float

phys.veloc.ang

(Mpc/h) (km/sec)

The Y-component of the spin of the subhalo.

spinZ

float

phys.veloc.ang

(Mpc/h) (km/sec)

The Z-component of the spin of the subhalo.

halfmassRadius

float

phys.size.radius

Mpc/h

Radius containing half of the mass of the subhalo.

vDisp

float

phys.veloc.dispersion

km/sec

The 1-D velocity dispersion of the subhalo, computed from all of the subhalo particles.